"Design problems with a blowout prevention system contributed to the 2010 Deepwater Horizon oil rig disaster, and the same equipment is still commonly used in drilling four years after the Gulf of Mexico oil spill, according to a report issued by the federal Chemical Safety and Hazard Investigation Board.

The board concluded that the "blowout preventer" — a five-story-tall series of seals and valves that was supposed to shear the drill pipe and short-circuit the explosion — failed for reasons the oil industry did not anticipate and has not fully corrected.

Despite improved regulation of deep-water drilling since the disaster, the board found that problems persist in oil and gas companies' offshore safety systems."